TestAsync

Make tests inside your ExUnit case to run async.

Installation

Available in Hex, the package can be installed by adding test_async to your list of dependencies in mix.exs:

def deps do
  [{:test_async, "~> 0.1", only: :test, runtime: false}]
end

Intro

As you might already know, ExUnit lets you define async test cases by providing an async: true option, like this:

defmodule App.FineTest do
  use ExUnit.Case, async: true

  test "one" do
    IO.inspect :one
  end

  test "two" do
    IO.inspect :two
  end
end

defmodule App.OtherTest do
  use ExUnit.Case, async: true

  test "three" do
    IO.inspect :three
  end
end

As described by the ExUnit documentation

async: true, runs the test case concurrently with other test cases. The individual tests within each test case are still run serially

That means, one and two will still be run one after the other.

If you’d want those two to be run concurrently, you’d have to create a new test case module for each.

This is exactly what TestAsync does, by providing a tiny macro test macro that will turn your ExUnit case tests into async cases.

Usage

Just use TestAsync !

defmodule App.FineTest do
  use ExUnit.Case
  use TestAsync

  test "one" do
    IO.inspect :one
  end

  test "two" do
    IO.inspect :two
  end
end

More examples as tests

Gotchas

Current module

If you use __MODULE__ on a test body, it will be the name of the generated case module and not the one of the parent module.

defmodule App.NamedTest do
  use ExUnit.Case

  test "one" do
    assert __MODULE__ == App.NamedTest.OneTest
  end
end

Setup functions

setup and setup_all are supported but only if they are given a function name. And setup_all is run for every test instead of just once as now every test was turned into its own test case.

Private functions

Private functions defined on the parent module cannot be seen inside the generated async modules.

defmodule App.SomeTest do
  use ExUnit.Case
  use TestAsync

  defp hidden, do: :ninja

  test "cant be seen" do
    assert hidden() # compile error
  end
end

Shared case template

However you can give use TestAsync a do block, which will be turned into a shared ExUnit.CaseTemplate.

defmodule App.NinjaTest do
  use ExUnit.Case

  use TestAsync do
    defp hidden, do: :ninja
  end

  test "can be seen" do
    assert hidden()
  end
end